The influence of seed quality on final yield of crops is well known. Seed priming is a naturally and environmental friendly way to improve the seed performance. It is effective for seeds with both low and high germination capacity. In seed priming, the basic metabolic reactions needed for the seed to germinate occur under conditions of high moisture, sufficient oxygen and suitable temperature. The germination process is typically interrupted by drying the primed seed before radical emergence, i.e. before the germination process is completed. Subsequently to drying the primed seed may be packed, stored, distributed and planted in the same manner as untreated seeds.
As have been established, seed priming has several advantages for crop production and forest planting. Primed seed usually results in more rapid and uniform emergence compared to unprimed seed. Further, primed seed germinated better across a wide range of temperature, adverse field conditions, such as salinity and limited water availability, than unprimed seeds. Priming also showed effect on breakdown seed dormancy in many vegetable species. The final yield increase by seed priming can lead to increased profits justifying the additional expense of priming treatment in many species. Thus there is a need for seed priming methods.
The priming methods of the art include hydro priming, osmotic priming and matrix priming. Among these priming methods, hydro priming has the advantage that saving both the cost for chemicals/matrix used during priming and labor to remove these materials after priming. However, hydro priming need more accurate technique to both produce good result and prevents seeds from germination during priming treatment. Further, it would be desirable to provide primed seed with improved shelf-life.
To prevent the seeds from germinating during the priming, the water supplied to the seed and the incubation time have to be strictly controlled.
JP7289021 discloses a process for unifying the germination starting period of a seed and providing a high-performance coated seed capable having improved and stabilized germination performance. In the disclosed process, the seed is immersed in water to make the water content of the seed ≥30% dry weight. The prepared seed is retained in a vapor-phase environment having ≥50% relative humidity until just before germination to provide a method for unifying the germination starting period of seed.
WO 99/33331 relates to a method for treating seed with a fluid, involving the use of a fluid-containing gas in a closed chamber containing one or more heat exchange surfaces. The treatment period length is of importance, where a longer period leads to unwanted germination and a shorter treatment is described to lead to inadequate synchronicity, i.e. a large number of seeds are still in the termination resting stage since they have not taken up enough water.
U.S. Pat. No. 6,421,956 discloses a method and apparatus for treating seed with a fluid, in particular water, involving the use of a fluid-containing gas, whereby seed is brought into contact with a gas having a controlled fluid content and the seed is kept in contact with the gas over a defined period whilst direct contact between the seed and the fluid in liquid form is substantially precluded. Prior to being exposed to fluid-containing gas, the seed may be wetted to lower the osmotic pressure of the seed.
U.S. Pat. No. 5,119,589 discloses a method wherein a seed is primed by progressive hydration in a rotating drum by water introduced as steam from a steam generator to condense as a mist on the drum walls or as liquid water pumped onto the drum walls through several fine bore tubes to form a surface film. The amount of water and its rate of addition are controlled such that the seeds remain free flowing. While offering control of the priming process, the slow hydration negatively affects the efficiency of the priming. The method further requires strict control of the progressive hydration. WO 96/08132 discloses a method where seeds and water are in contact through a semi-permeable membrane, resulting in a slow hydration negatively affecting the priming and requiring strict control of the osmotic potential in the water.
Other examples include U.S. Pat. No. 5,232,465, which discloses a method where populations of grass seeds are subjected to a plurality of alternating hydration and dehydration periods. The alternation of hydration/dehydration periods pose a risk, as seeds made delicate by a high moisture content are periodically harshly treated by low humidity air. Furthermore, the high humidity air (RH 93-98%) periods require careful control for seed not to germinate.
In these methods, if the seeds were saturated when contacted with water/fluid, the incubation time should be strictly controlled to prevent seeds germination during priming. If the imbibitions were aborted before the seeds being saturated, the limitation of water, especially embryo which is usually situated inside the endosperm or pericarp, limits the priming effect. Removing the seeds too early from imbibitions, may lead to even poorer germination performance than unprimed seeds.
Finally, WO 08/153388 discloses a method of priming seed, wherein not water but rather partial oxygen pressure and/or partial carbon dioxide pressure is used to control the priming process. Limiting the availability of oxygen during the incubation may negatively affect the priming.
Thus, there is a need for a seed priming method overcoming deficiencies of the art.